Extremely Subtle Ownership Signs

Is there any method or symbol that allows a keyholder to signal ownership without it being too obvious in everyday life? Perhaps something like a collar, but not overly BDSM-style? Most ideas I can think of revolve around the KH’s actions, such as her holding onto the key.

What about designing a bracelet? It could be quite affordable, similar to those rubber wristbands worn for charity causes. Or perhaps something crafted from Stainless Steel (are you listening MM & Steelworxx)? If it isn't too flashy, I'd definitely wear one.

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The wedding ring is amusing, but it doesn't fully convey the power dynamic we're aiming for.

Eternity Collars provides a collection of locking slave bracelets made from various metals and finishes. This selection of symbolic jewelry can be seen here: Each bracelet includes two Allen wrenches and two locking screws, with one screw used to secure the piece on the wearer.

My wife purchased a silver choker chain for this specific purpose. Initially, I removed it when sleeping or showering, but as our dynamic evolved, it gained more significance and now stays on constantly unless she removes it to polish it. People have noticed it, including her boss! They ask if there is special meaning behind it since they see me wearing it daily regardless of my outfit. Usually, saying it was a gift from her suffices, and most accept this explanation without further thought.

Isn't what the OP seeks essentially the core function of a chastity device?